Centering for concrete or masonry arches.



UNITED sTATEs PATENT oEEIcE.

Wil-BUB I- WATSON, or EAST CLEVELAND, onto.

GENTERNG POB CONCRETE OR MASONRY ARCHES.

Specieation of Letters Patent. apuestan and January a7. `1911.v serialnu. 604,974.

Patented Aug. 26j, 191.3'.

To all' whom, it may. concern Be it known that I', WILBUR Je WarsoN, avcitizen of the United States, residlng at East Cleveland, in the countyof Cuyahogal center-ings for concrete or masonry arches,

and particularly for long. span arch bridges.

@ne of the objects of the invention is to lessen the cost ofconstruction and erection 18 of centerings and to provide a centeringwhich can be used repeatedly.

A further object is to provide a centering which has a minimumdeiiection when. the load is applied and which is especially adapted forsituations requiring a large-unobstructed opening for the flow of wateror to avoid the obstruction of navigation in case the bridge is to beconstructed` over a navigable stream.

The centering constructed in accordance withmyinvention consists of anarch which is of the three-point-pin type and is composed of twosections suitably constructed, and connected together at their upperends in the center plane of the arch by a single pin, and at their lowerends, the said sections are each connected by a single pin to a suitablesupport, which I term a shoe.

The invention may be further briefly summarized as consisting in certainnovel details of construction and combinations and arrangements of partswhich will be described in the specication and set forth in the appendedclaim.y

In the accompanying sheet of drawings, the single ligure is a sideelevation of a concrete arch bridge with my improved centering, ortemporary false-work in position.

Referring now tothe drawing, 10 represents the two abutments or piersfor the concrete arch bridge 11 which is supported until set or untilself supporting by my improved centering. 0n the inner faces of theabutments 10 are bases 12 for the centering, which bases may be formedof masonry either integral with or independent of the abutments or maybe formed by cantaliverin steel beams out from the abutments.

he centering or false work which I employ consists of two braced arches13, each of-whicli is 'preferably formed of steel or combined steel and'timber and the whole structure. beingro what I term. thethreepoint-pinned type,'inasmuch asit consists of two unitary/section13, 13, which are pinned together at their upperends or at thetop'of-the arch `1.?) by meansof a pin 14 and: at their lower ends areconnectedby pinsV 15 to ordinary-bridge shoes 16 which restupcn loweringdevices, each sectiony being connected` atits lower end by a single pintooneof-tlie shoes 16. It is to be-understood that these pins 145 and 15at the top and lower ends of the sectionsr are not for hingingpunposes,as the sections are not at any time intended to be moved inwardly or y youtwardlywith respect to-cach other, but the two pinned sections areemployed not only for convenience in the erection and removal of: thecentering but the pins confine the stresses which are transmittedbetween the two sections and between the lower ends of the sections andthe shoes 16 to the three points. Eachof the sections 13 consists of astraight lower chord- 17, a series of comf paratively short upper chords18 and a plurality of bracing members 19am-.anged-7 be tween the upperand lower chords. On .top of they arches 13 and arranged at regularintervals are cross beams 20 on which are placed bows 21 formedpreferably of timber and on top of the bows is laid lagging 22 uponwhich the concrete of the main arch 11 is placed.

After the concrete arch has set, and is self supporting, it isdesirable, if not necessary, that the centering be lowered from theconcrete arch as a unit, so that the arch can gradually assume itspermanent position, it being understood that when the centering isremoved, the arch settles a Small amount, the exact amount dependingupon the design and span of the arch. Consequently, between the shoes 16and the abutments 12, I provide suitable'lowering de` vices, each ofwhich may bedesignated as a whole by the reference character 23. Theselowering devices do not constitute parts of the present invention, andneed not be explained in detail, nor further illustrated. It will beunderstood that thereV will be employed appropriate lowering deviceswhich will enablev the entire centering to be lowered gradually anduniformly.

I may, if desired, employ steel tie rods 28 between the ,lower ends ofeach of the arches 13, but except in special cases, these bled. Afterthe cross beams, bows and lag-V ging are in position, the concrete ormasonry arch 11 is built, this arch being preferably built in sections.Preferablythe top sections 11'* find 11" of the arch .11 are first iplaced in position in order that the centerlng frames will be brought toa good-bearing. Then the sections at the quarterpoints are placed linposition and afterward the other sections are placed in position in apredetermined order. v

After the concrete arch has been built and the centering has been left'in osition, the required len-h of time to enagle the arch to obtain sucient strength to be 'self sup-V porting, the centering is lowered inthe manner above stated. The centering may then be -removed from thesite of the bridge and used again for similar structures at otherlocations.

The character of the steel or steel and timber arches 13 is such that asthe load is applied to them, there is a minimum deflection,

`signature in the the stresses being carried principally by the topchord members. 'This isan extremely desirable feature for this class ofwork. Furthermore, not only is the deection very slight, but thecharacter of the centering is. such that a large o en space is leftbelow the concrete arch or Athe iiow of water, the level of which i'sindicated by the line 29. Furthermore, the centering need not obstructor interfere with navigation, in view of the fact that at least at thecenter of the stream, the distance from the normal water level to thecentering is almost the same as to the concrete arch itself.

Having thus described my invention, what I claim is A centering ortemporary false work for masonry or concrete arches com rising athree-point-pinned arch comp -of two sections supported solely at theirlower ends and connected together at their upper ends at the; centerplane of the arch bya single pin through which stresses are transmittedfrom one section to the other, supports at the lower ends of thel twosections each connected to the corresponding section by a single pin.

In testimony whereof, I hereunto aiiix my presence of two witnesses. yWILBUR J. WATSON. Witnesses:

H. R. SULLIVAN, A. J. HUDSON.

